The Atmosphere

Question 1

Definition of atmosphere

Answer 1

• envelope of gas
• essential to life on Earth - to breath and protect from radiation
• mainly consists of nitrogen (N2) and oxygen (O2)

Question 2

What layers are there in teh atmosphere?

Answer 2

Thermophere
Mesopause
Mesosphere
Stratopause
Stratosphere
Tropopause
Troposphere

Question 3

Describe the Thermosphere

Answer 3

around 90-700 km

• very low density and pressure
• mainly made up of atoms and ions as the molecules are broken appart by high temp UV solar radiation
• strong influence of solar activity - high temp
• no water vapour
• theoretically part of the atmosphere but often concidered as outer space

Question 4

Describe the Mesosphere

Answer 4

around 50-90 km
- mesopause generally concidered the edge of space
- relatively light concentration of iron and other metal atoms
- strong influence of waves and tides: coupling mechanisms
- polar clouds
impact on climate change as high energy solar particles interact with molecules

Question 5

Describe the Stratosphere

Answer 5

around 15-50 km

• very high verticle stability ( < 0) - inhibition of vertical motion
• long residence time of gas molecules or aerosols entering the stratosphere - several years
• ozone layer

Question 6

Describe the ozone layer

Answer 6

In the stratosphere - around 25 km

• stong increase in the O3 concentration
• absorbs solar UV incoming radiation via photochemical reactions
• ozone hole - local and seasonal over arctic due to the release of halogen compounds by human activities

Question 7

Describe the Troposphere

Answer 7

0-15 km

• mixing layer
• unstable layer - important veticle mixing (convecting and turbulent processes)
• almost all weather occurs within the troposphere
• most of the mass in the atmosphere (75-80%)
• contains almost all water vapour
• planetary boundary layer (PBL)

Question 8

Describe the planatery boundary level

Answer 8

PBL
- lower part of the troposphere, where the surface strongly influences temperature, moisture and wind

Characteristics:

• turbulence and rapid verticle mixing
• varying height (20-200m)
• often topped by an inversion layer that has less exchange with free atoms

Question 9

Explain the energy budget of the earth

Answer 9

Earths atmosphere system absorbs electromagentic radiation and emits it at a longer wavelength.
Total SW rad (solar) = total emitted LW (IR) rad

Not in balance at local level
- lower latitudes more energy (equator) because of larger angles that the sun emits and less area to cover

The uneven heating on earths surface casuses mass movement fo air and water

Question 10

TF: what is the Coriolis force? Explain what it is due to, on which kinds of bodies it acts, how it changes with latitude and influence on wind, in each hemisphere.

Answer 10

The Coriolis force is a fudge factor, allowing us to ignore in equations for motion that the earth is rotating.
It acts only in the horizontal plane
Northern hemisphere: 90 degrees to the right of the velocity of a moving air parcel
Southern hemisphere: 90 degrees to the left

The Coriolis force starts at 0 degrees at the equator and increases towards the poles as the radius from you to the earths axis decreases.

Question 11

TF: Winds on a global scale
Draw a clear picture representing the global atmospheric circulation. These pieces on info must appear:
- verticle circulation patterns (wind directions)
- horizontal surface wind patterns
- approx latitudes where an inversion of wind is observed

Answer 11

Pressure:
High - Low 60d - High 30d - Low 0d - high 30d - Low 60d - high

Horizontal winds, starting from equator
North of eq - going down right to left

Verticle winds, from north, right side:
Going down from top
- polar cell, ferrel cell, hadley cell

Question 12

TF: how do you explain that the sky is blue while clouds are white?

Answer 12

Because the diff particles in the sky scattering different wavelengths of light.

Question 13

TF: What do we call an “atmospheric window”?

Answer 13

An atmospheric window is where no gases in the atmosphere absorb or emitt light/radiation in the radioation frequency and IR radiation goes right through the greenhouse gases.

Question 14

TF: What are the two main atmospheric compounds?

Answer 14

Nitrogen N2 - 78%

Oxygen O2 - 21%

Question 15

TF: What do we call trace gases?

Answer 15

Trace gases are gases in the atmosphere which there is a low perentage of, < 1%. They give the greenhouse effect.
ex: CO2 (biggest), Ozone O3, Helium H2, Methane CH4, H2O water vapour

Question 16

TF: Explain why trace gases play an important role in the atmospheric system

Answer 16

• they absorb and emitt IR light
• protect against harmful UV radiation
• needed for ecosystem (esp. CO2 and water)

Question 17

TF: Define the term aerosol. Give examples and their sorces.

Answer 17

Aerosol = fine solid particles or liquid droplets suspended in the air

ex: 
sulfate - coal fire plants
sulfur dioxide - volcanoes
nitrates
NOx - from fuel burning

Question 18

TF: Define lapse rate

Answer 18

Lapse rate = rate of decrease of temperature with hight

If the lapse rate is below zero (<0) then the atmospheric layer is stable. Above zero (>0) the layer is instable with turbulence and verticle mixing

Question 19

TF: What can you say about the lapse rate in the different atmospheric layers?

Answer 19

Thermosphere <0
Mesosphere >0
Stratosphere <0
Troposphere >0

Question 20

TF: What is the intertropical convergence zone (ITCZ)? What can you say about the wind and the typical weather in this region?

Answer 20

• The ITCZ is a band of low pressure around the earth, it lies near to the equator
• the trade winds of the north and south hemisphere come together here, which leads to frequent thunderstorms and heavy rain.
• Characterised by weak and erratic horizontal winds and intense connective activity
• leads to wet and dry seasons as it moves over the year.. during July it is closer tot he equator and in January it is a bit more to the south. This is because it is influenced by ocean currents and mountain ranges.

Question 21

TF: Explain meaning of “geostrophic approximation”.

Answer 21

Geostrophic approximation = balance between the horizontal pressure gradient and Coriolis force. They are equal in magnitude but opposite directions.